Subject: Re: mechanical cochlear model From: Martin Braun <nombraun@xxxxxxxx> Date: Wed, 2 Jun 2010 17:31:33 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear Peter and others, Thank you for the comment. It gives us the opportunity to further clarify the issue. There are two possible types of "motion of the fluid" in the joint scala vestibuli and vestibule chamber that can be caused by stapes motion: Type A motion If the stapes pushes into the scala vestibuli like a piston, it instantaneously increases the pressure at any place in the fluid chamber almost simultaneously. This pressure increase, if it is big enough, can move the basilar membrane (BM). Type B motion If the stapes just vibrates without causing fluid bulk shift, and thus without causing a global pressure change in the fluid chamber, there might not be enough energy propagating through the fluid that could move the BM. At the same time there might be enough energy propagating through the fluid for a motion of the cilia of the hair cells. Would this answer your question? Martin --------------------------------------------------------------------- Martin Braun Neuroscience of Music S-671 95 Klässbol Sweden email: nombraun@xxxxxxxx web site: http://www.neuroscience-of-music.se/index.htm ----- Original Message ----- From: "Peter van Hengel" <pwj.vanhengel@xxxxxxxx> To: <AUDITORY@xxxxxxxx> Sent: Wednesday, June 02, 2010 12:46 PM Subject: Re: mechanical cochlear model Dear Martin, interesting results no doubt, but once again I must protest against the conclusions. As I have stated before it is not so easy to abolish or greatly reduce the traveling wave in the cochlea. Any motion of the fluid, in combination with the flexibility of the BM, will cause a traveling wave, even if you severely influence the boundary conditions. Oversimplification of fluid mechanics in the cochlea has led to erroneous conclusions before... Just a warning against drawing conclusions too rapidly. Regards, Peter 2010/6/2 Martin Braun <nombraun@xxxxxxxx> > Dear List, > > New data have appeared that are again consistent with each of the > following > two hypotheses: > > A. Cochlear macromechanics has no role in hair cell excitation near > threshold of hearing. > B. Cochlear macromechanics has an important role in hair cell protection > at > excessively high sound levels. > > http://www.neuroscience-of-music.se/Sohmer2.htm > > Enjoy, > > Martin > > > --------------------------------------------------------------------- > Martin Braun > Neuroscience of Music > S-671 95 Klässbol > Sweden > email: nombraun@xxxxxxxx > web site: http://www.neuroscience-of-music.se/index.htm > > > > > > ----- Original Message ----- From: "Martin Braun" <nombraun@xxxxxxxx> > To: <AUDITORY@xxxxxxxx> > Sent: Saturday, March 06, 2010 10:29 PM > Subject: Re: mechanical cochlear model > > > While the cochlear traveling wave has appeared in numerous empirical > reports > on real physical models and real biological animals, it's function in > hearing is not yet universally appreciated. Some people still think that > it > provides the well known frequency selectivity that we observe in the > auditory nerve. This view, however, has been proved wrong by multiple > direct > experimental evidence. Just consider two bodies of evidence: > > 1) Hearing sensitivity is not affected, when endolymphatic hydrops presses > the basilar membrane flat upon the bony cochlear wall of the scala > timpani: > > http://www.neuroscience-of-music.se/Nageris.htm > > http://www.neuroscience-of-music.se/Xenellis.htm > > > 2) It is a well established observation for more than 50 years that > closure > of the round window does not affect hearing sensitivity. This means that a > pressure difference across the basilar membrane and a resulting traveling > wave cannot be a necessary condition of hair cell excitation. Recently, > Perez et al. (2009) reported that closure of the round window not only > leaves hearing sensitivity unchanged but increases cochlear vulnerability > at > high sound levels. This second new observation is a further compelling > indication as to the real function of the cochlear traveling wave. > > http://www.neuroscience-of-music.se/Sohmer.htm > > > Martin > > > --------------------------------------------------------------------- > Martin Braun > Neuroscience of Music > S-671 95 Klässbol > Sweden > email: nombraun@xxxxxxxx > web site: http://www.neuroscience-of-music.se/index.htm